本试验旨在研究3种粗饲料（燕麦草、青贮玉米和苜蓿，其中苜蓿添加比例恒定为10%，青贮玉米+燕麦草添加比例恒定为60%）饲喂斯布牦牛的组合效应，并对不同组合饲粮进行营养物质表观消化率测定，筛选出适宜斯布牦牛采食的组合饲粮。选用体重相近的干奶期斯布牦牛30头，随机分为5组，每组设2个重复，每个重复3头牦牛，进行消化试验。配制5种试验饲粮，其组成如下：Ⅰ组，60%燕麦+10%苜蓿+30%精料；Ⅱ组，45%燕麦+15%青贮玉米+10%苜蓿+30%精料；Ⅲ组，30%燕麦+30%青贮玉米+10%苜蓿+30%精料；Ⅳ组，15%燕麦+45%青贮玉米+10%苜蓿+30%精料；Ⅴ组，60%青贮玉米+10%苜蓿+30%精料。结果显示：Ⅲ组的采食量、总增重最高，料重比最低。Ⅰ、Ⅱ、Ⅲ组粗蛋白质和粗灰分表观消化率显著高于Ⅳ、Ⅴ组（P<0.05）；Ⅳ组中性洗涤纤维表观消化率显著高于Ⅰ、Ⅱ、Ⅲ组（P<0.05）；Ⅲ组酸性洗涤纤维表观消化率显著高于其他各组（P<0.05）；Ⅰ、Ⅱ组钙表观消化率显著高于Ⅴ组（P<0.05）；Ⅳ组总磷表观消化率显著高于Ⅱ、Ⅴ组（P<0.05）。以青贮玉米添加比例作为自变量（X），以粗蛋白质和中性洗涤纤维表观消化率分别作为因变量（Y）去拟合模型，得到三次方程，自变量与因变量之间均呈强相关关系，相关系数（R²）分别为0.987和0.937。由此得出，燕麦草与青贮玉米的混合饲喂对斯布牦牛营养物质表观消化率具有组合效应，当青贮玉米添加比例为30%、燕麦草添加比例为30%时，斯布牦牛的料重比、增重及饲粮中各营养物质的表观消化率达到较好的效果，尤其是蛋白质和纤维的利用。

In order to seek optimal feed formula that is suitable for Sibu yak, this experiment was conducted to study the combination effect of 3 roughages (oat, silage corn and alfalfa, the adding proportion of alfalfa was fixed 10%, and the adding proportion of oat+silage corn was fixed 60%), and to measure the nutrient apparent digestibility of various combination diets. A total of 30 Sibu yak with similar weight were selected for digestion experiment, and those were divided into 5 groups with 2 replicates per group and 3 yak per replicate. Five experimental diets were formulated, the composition of them were as follows:group Ⅰ, 60% oat+10% alfalfa+30% concentrate; groupⅡ, 45% oat+15% silage corn+10% alfalfa+30% concentrate; group Ⅲ, 30% oat+30% silage corn+10% alfalfa+30% concentrate; group Ⅳ, 15% oat+45% silage corn+10% alfalfa+30% concentrate; groupⅤ, 60% silage corn+10% alfalfa+30% concentrate. The results showed as follows:the feed intake and total body weight gain in group Ⅲ had the highest values, while the feed/gain had the lowest value. The apparent digestibility of crude protein and ash in groups Ⅰ, Ⅱ and Ⅲ was significantly higher than that in groups Ⅳ and Ⅴ (P<0.05), the apparent digestibility of neutral detergent fiber was significantly higher than that in groups Ⅰ, Ⅱ and Ⅲ (P<0.05), the apparent digestibility of acid detergent fiber was significantly higher than that in other groups (P<0.05), the apparent digestibility of calcium in groups Ⅰ and Ⅱ was significantly higher than that in group Ⅴ (P<0.05), and the apparent digestibility of total phosphorus in group Ⅳ was significantly higher than that in groups Ⅱ and Ⅴ (P<0.05). When the adding proportion of silage corn as independent variable (X), the apparent digestibility of crude protein and neutral washing fiber as dependent variables (Y), three regression equations were established and the correlation coefficients (R²) were 0.987 and 0.937, respectively, which indicated a strong correlation between independent variable and dependent variables. In conclusion, silage corn combined with oat has combination effect on nutrient apparent digestibility of Sibu yak, when the adding proportion of silage corn is 30% and the adding proportion of oat is 30%, the indexes of feed/gain, weight gain and nutrient apparent digestibility of Sibu yak can be achieved a better effect, especially the utilization of protein and fiber.